1. Field of the Invention
The present invention relates generally to the transfer of signals between an codec and a codec controller through an AC-link bus, and specifically to a system and method for reconfiguring the protocol of the AC-link bus to allow digital subscriber line (DSL) modem communication over the AC-link bus.
2. Description of Related Art
Personal computers are currently being used for a wide variety of multimedia applications, where it is now becoming desirable for personal computers (PCs) to function with high quality audio performance. Current PC audio architectures are designed to run midrange audio-performance-integrated ISA products. In order to provide PCs with high performance/high quality audio comparable to electronics devices, a new PC architecture capable of providing this performance needed to be developed. Thus, a computer industry consortium developed a new PC audio architecture, the Audio Codec ""97 (AC ""97), for next-generation audio-intensive PC applications, such as DVD, 3-D multiplayer games, interactive music, and up to 2 line V.90 modems. The AC ""97 architecture defines a high quality audio architecture for a PC platform to support a wide range of high quality audio solutions, from a 2-channel mix of digital and analog audio inside the PC to multi-channel audio outside the PC. The AC ""97 includes at least one codec and codec controller. The codec includes two separate chips, one for primarily analog applications and one for primarily digital applications. By separating the functions performed between the analog and digital chips, individual yields can be improved which lead to overall cost reduction for the system.
The codec 10 performs digital-to-analog conversion (DAC) and analog-to-digital conversion (ADC), mixing, analog processing, and modem codec functions. The codec 10 functions as a slave to a digital codec controller 12, which, in turn, is connected to the CPU 14 of the PC, as shown in FIG. 1. The codec 10 communicates with the codec controller 12 through a digital serial link, referred to as the AC-link bus 16. The codec 10 performs the appropriate data conversion and communicates analog signals to an input/output device 18. The AC-link bus 16 was designed to directly connect the codec 10 to the codec controller 12. In prior PC architectures, it was necessary to connect an interface device between a codec 10 and the core logic controlling the codec 10. The AC ""97 eliminates the need for a separate interface device to be incorporated by utilizing the AC-link bus to directly connect the codec 10 to the codec controller 12.
The AC-link bus 16 is a bi-directional, 5-wire, serial time-division multiplexed (TDM) interface designed for a dedicated point-to-point interconnect, as illustrated in FIG. 2. All digital audio streams, modem line Codec streams, and command/status information are communicated over the AC-link bus in data packets. The AC-link bus architecture has a defined protocol which divides each data packet into 12 outgoing and 12 incoming data streams, each with 20-bit sample resolution. Each of the data streams are positioned in a respective one of the 12 TDM slots in the data packet, as shown in FIG. 3. The output data streams correspond to the multiplexed bundles of all digital output data targeting AC ""97""s DAC inputs and control registers. The AC-link bus protocol is set forth in the Audio Codec ""97 Component Specification, Revision 1.03, released Sept. 15, 1996 by the Audio Codec ""97 Working Group, Audio Codec ""97, Revision 2.0, released Sep. 29, 1997 by Intel Corporation, and Audio Codec ""97, Revision 2.1, released May 22, 1998 by Intel Corporation. The disclosures of Revisions 1.03, 2.0, and 2.1 of the Audio Codec ""97 are hereby incorporated by reference into this disclosure.
The industry consortium developing the AC ""97 architecture wanted to promote interoperability between codecs 10 and codec controllers 12 produced by different vendors to function according to AC-link protocol. Thus, strict adherence to the specified audio input and output frame slot definitions, AC-link bus protocol, and electrical timings are required for interoperability to be maintained between various codecs 10 and codec controllers 12. The AC-link bus 16 basically performs one function, it transmits the data streams in the data packets defined by the AC-link protocol between the codec controller 12 and the codec 10, so that the AC-link bus 16 merely provides a direct data link between the codec 10 and the codec controller 12.
The codec 10 may be connected to a plurality of possible input/output devices 18, including a telephone line to communicate modem data. Modems are utilized to perform data transmissions between devices attached to the telephone line. There has recently been a growth in need for high-speed data-transmission technologies, where digital subscriber line (DSL) modem technology has been developed to deliver high bandwidth transmissions over conventional copper telephone wiring at limited distances. DSL technology utilizes a pair of devices having matched circuitry components connected through a telephone line, with one DSL modem located at the telephone company central office and the other DSL modem located at a customer""s local site. The special matched circuitry provided in the DSL modems allows high-speed transmissions to occur between the two modems over a telephone line. Various types of DSL technology transmissions have been developed, including asymmetric DSL (ADSL), high-data-rate DSL (HDSL), single-line DSL (SDSL), and very-high-data-rate DSL (VDSL). The various DSL technologies are capable of transmissions at rates from 1.5 Mbit/s and up.
A problem existing with the protocol for the AC-link bus 16 is that this protocol is not designed to handle such high bandwidth DSL transmissions over an AC-link bus 16. The AC-link bus protocol provides for one of the 12 defined TDM slots in the data packet to contain a data stream for each communication line, where up to two communication lines can be supported by the AC-link bus protocol. In the industry-defined AC-link bus protocol data packet shown in FIG. 3, slot number 5 is assigned to handle respective data streams for a modem connected to a first communication line in both the incoming and outgoing data packets while slot number 10 is assigned to handle respective data streams for a modem connected to a second communication line. Presently, most personal computers are equipped with modems capable of data transmissions at rates no faster than V.90 protocol, i.e., up to 56 Kbit/s. While the bandwidth capabilities of a single TDM slot in the AC-link bus data packet is capable of handling such 56 Kbit/s data rates, the AC-link bus protocol does not allow high bandwidth DSL transmissions of 1.5 Mbit/s or greater to occur over the AC-link bus. DSL transmissions are not supported by the AC-link bus protocol, since the designated modem TDM data slot in the AC-link bus data packet is not capable of handling the high bandwidth requirements of a DSL transmission.
There is clearly a need for a system and method for performing a DSL technology modem transmission over an AC-link bus. Moreover, there is a need for a system and method for redefining the AC-link bus protocol in order to allow a high bandwidth DSL technology modem transmission to be performed over an AC-link bus.
It is a primary object of the present invention to overcome the aforementioned shortcomings associated with the prior art.
The present invention provides a system and method for system and method for performing a DSL technology modem transmission over an AC-link bus.
The system and method for performing a DSL transmission over an AC-link bus redefines the protocol of the AC-link bus in order to allow a high bandwidth DSL transmission to be performed using the data streams in a data packet transmitted between a codec and a codec controller over the AC-link bus. The codec and codec controller connected to the AC-link bus are configured for a particular AC-link bus protocol defining a data packet having multiple time-division multiplexed (TDM) data slots, so that these devices recognize which type of data stream appears in the separate TDM data slots of a data packet communicated over the AC-link bus. Currently, the AC-link bus protocol defines twelve (12) TDM data slots, where each data slot is assigned a respective data stream accomplishing a particular function. The AC-link bus protocol only provides one of the data slots for handling a modem data stream for each communication line.
The present invention redefines the AC-link bus protocol to provide at least one additional data slot for handling modem data stream transmissions. The additional data slot provides additional bandwidth capabilities which allows high-bandwidth DSL modem transmissions to be sent in the data packets transmitted over the AC-link bus. The additional TDM data slots in the data packet redefined for a DSL modem transmission may be provided in a number of ways. The system may monitor the data packet to determine whether any of the TDM data slots are not being used, where the system redefines the unused data slots to communicate DSL transmission data. Alternatively, the system of the present invention may compress and combine multiple TDM data slots into a single data slot in order to make additional data slots available for DSL transmission data. It is also possible to simply eliminate data streams in a certain TDM data slot and replace the data stream with DSL transmission data.
For high bandwidth DSL transmissions, an alternative embodiment of the system of the present invention utilizes an AC-link bus having a redefined protocol in conjunction with a USB bus to provide additional bandwidth capabilities for the DSL modem transmission. In still another alternative embodiment, undefined sideband signals for an Audio/Modem Riser (AMR) can be used in conjunction with the redefined protocol for the AC-link bus to provide the additional bandwidth capabilities necessary for high data-rate DSL modem transmissions.